68 lines
1.3 KiB
Plaintext
68 lines
1.3 KiB
Plaintext
pub opaque type AssocList<key, value> {
|
|
inner: List<(key, value)>,
|
|
}
|
|
|
|
pub fn new() -> AssocList<key, value> {
|
|
AssocList { inner: [] }
|
|
}
|
|
|
|
pub fn from_list(xs: List<(key, value)>) -> AssocList<key, value> {
|
|
AssocList { inner: do_from_list(xs) }
|
|
}
|
|
|
|
fn do_from_list(xs: List<(key, value)>) -> List<(key, value)> {
|
|
when xs is {
|
|
[] ->
|
|
[]
|
|
[(k, v), ..rest] -> do_insert(do_from_list(rest), k, v)
|
|
}
|
|
}
|
|
|
|
pub fn insert(
|
|
in m: AssocList<key, value>,
|
|
key k: key,
|
|
value v: value,
|
|
) -> AssocList<key, value> {
|
|
AssocList { inner: do_insert(m.inner, k, v) }
|
|
}
|
|
|
|
fn do_insert(elems: List<(key, value)>, k: key, v: value) -> List<(key, value)> {
|
|
when elems is {
|
|
[] ->
|
|
[(k, v)]
|
|
[(k2, v2), ..rest] ->
|
|
if k == k2 {
|
|
[(k, v), ..rest]
|
|
} else {
|
|
[(k2, v2), ..do_insert(rest, k, v)]
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn union(
|
|
left: AssocList<key, value>,
|
|
right: AssocList<key, value>,
|
|
) -> AssocList<key, value> {
|
|
AssocList { inner: do_union(left.inner, right.inner) }
|
|
}
|
|
|
|
fn do_union(
|
|
left: List<(key, value)>,
|
|
right: List<(key, value)>,
|
|
) -> List<(key, value)> {
|
|
when left is {
|
|
[] -> right
|
|
[(k, v), ..rest] -> do_union(rest, do_insert(right, k, v))
|
|
}
|
|
}
|
|
|
|
fn fixture_1() {
|
|
new()
|
|
|> insert("foo", 42)
|
|
|> insert("bar", 14)
|
|
}
|
|
|
|
test union_1() {
|
|
union(fixture_1(), new()) == fixture_1()
|
|
}
|